Recent years, it has been recognized as a problem that asthma or allergy caused by allergens contained in tick excrement, carcass thereof, cedar pollen, and so on. Allergen is defined as a protein which reacts specifically with antibody of human (meaning of the protein includes glycoprotein). Along with recognition of such a problem, it has been increasingly interested in the influence of living environment on human health. Thus, the way to manage a household allergen has been recognized as a major issue for interior manufacturers or building product manufacturers.
It has been expected to use a photocatalyst material for handling materials including the household allergens. The photocatalyst material expresses oxidatively decomposing activity about some inorganic substance such as nitrogen oxide and organic substance, by utilizing light as energy source. Note that, light is low in its generating cost, and affects little load on the environment. Recently, thus, many studies have been carried out to apply photocatalyst materials to environmental cleaning, odor elimination, dirt elimination, sterilization, and so on. The photocatalyst material is also expected to degeneratively decompose the allergen.
Titanium oxide has been widely known as photocatalyst which exhibits activity under irradiation of UV-ray. However, photocatalyst material has need to exhibit the activity under irradiation of visible light in order to perform its function in interior of building, and therefore, such a photocatalyst material has been studied and developed.
For example, patent document 1 discloses a photocatalyst material exhibiting visible-light activity, which is composed of titanium oxide crystal in which oxygen atom sites are partially displaced by nitrogen atoms.
In the photocatalyst material disclosed in patent document 1, a part of oxygen atom sites of titanium oxide crystal are displaced by nitrogen atoms to make a new isolated level in the bandgap of titanium oxide, thereby the photocatalyst material is to exhibit the visible-light activity. When being exposed by a photon having energy larger than the bandgap energy between the isolated level and conduction band of titanium oxide, an electron in the isolated level is excited to the conduction band and a hole is generated in the isolated level, thereby the photocatalyst material exhibits the activity.
Patent document 1: Japanese patent publication No. 3601532